The Western Schism was a split between factions of the Roman Catholic Church between 1378 and 1417.[1]

During this period, more than one claimed to be the true pope.[1]

The reasons for the split were mostly political, rather than theological. The Council of Constance (1414–1418) ended the schism when they elected Martin V as the new pope.

"Western Schism" . Catholic Encyclopedia. New York: Robert Appleton Company. 1913.

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